Many schools are still being built without mechanical ventilation and only windows are used to bring in outdoor air. This contravenes the German Energy Saving Ordinance (EnEV), which requires the building envelope to be airtight. It also means that on cold days ventilation is far from adequate. As a result, the concentration of CO₂ is well above permissible levels and pupils are less alert. These facts have been known for many years but are often ignored for cost reasons. Due to the coronavirus pandemic, however, they have taken on a whole new priority. The intelligent CONCRETCOOL concrete core cooling ventilation system provides a sustainable solution.

At present, many people are looking at schools with concern and considering how the risk of infection there can be kept low. One frequently discussed problem is the need for ventilation in buildings which do not have mechanical ventilation. During winter in particular, exchanges of air are often too short and therefore mostly inadequate. If there is a Covid positive pupil in such a room, poor ventilation means that the concentration of virus-laden aerosols will continually increase. This also drastically raises the risk of infection for the other children. There is now so much hype about air quality in schools that countless more or less usable air purification systems are quickly being brought to market. Kiefer Klimatechnik developed CONCRETCOOL concrete core cooling with supply air 20 years ago. The concrete core cooling ventilation system has since proven its worth many times over and is particularly suitable for new school and office buildings. It features the ideal combination of two important aspects: stale, aerosol-laden air is replaced with fresh, clean outdoor air while at the same time focusing on energy efficiency.

Unique dual function of building services
The special feature of CONCRETCOOL is that outdoor air serves as the heat transfer medium – rather than water which is more typical – and this can be used to directly cool the concrete ceilings without any additional energy consumption. While the supply air initially streams through the cooling tubes in the concrete ceilings, it warms to approximately the same temperature as that of the ceiling. The supply air is then fed to the interior via Kiefer air diffusers, providing the fresh air changes inside the building which are necessary to meet hygiene requirements. Thermal building component activation also makes it possible to use the building mass to store energy – a key benefit because the energy efficiency requirements for new buildings are rising all the time. Heating and cooling technologies which conserve resources are therefore becoming increasingly important, as are renewables. The way the CONCRETCOOL ventilation system works is similar to the hot air heating invented by the ancient Romans. In that case, hot air was streamed through solid components such as walls, floors or benches. Whereas in antiquity an outside furnace served as the energy source, CONCRETCOOL uses the outdoor air’s cooling potential. This uses up to 50 percent less energy compared to conventional systems that have water as the energy source.

A central supply of fresh air keeps pupils alert during lessons
Even before the coronavirus pandemic, there was a lack of fresh air in many classrooms across Germany. The maximum recommended level of 1000 ppm CO₂ in the air that pupils breathe is still exceeded in many places. Tiredness and difficulty concentrating are known effects. Some end clients and planning offices have considered this issue in the past and acted early by installing a concrete core cooling ventilation system. At the Grimmelshausen grammar school in Gelnhausen near Frankfurt am Main, the design engineers chose CONCRETCOOL to provide a central supply of fresh air. The supply air is not fed directly to the room; it first flows through aluminium cooling tubes embedded in the concrete ceiling and cools the ceiling. This warms the air to a pleasant 21 °C without the need for supplementary heating. The school thus benefits from low operating costs and maximum energy savings as well as hygienically ventilated classrooms. The design for the Herwig Blankertz and Max Born vocational college in Recklinghausen also took a long-term, sustainable view. An integral energy and building concept was developed to create a comfortable and hygienic ambient climate, which is conducive to focused working at any time of day and during any season of the year. In addition to the dual shell building envelope, the CONCRETCOOL ventilation system has a central role along with a replacement air system. For 70 percent of the year, the outdoor air is below 12 °C and is therefore available already cool and free of charge – making it ideal for supplying fresh air to classrooms.

Aesthetics are a plus point alongside hygiene and sustainability
It is a common requirement on new build projects that the ventilation systems do not compromise the architectural design. For example, the architects for the Sebastian Lotzer middle school in Memmingen wanted smooth concrete ceilings throughout. This was an ideal scenario for the CONCRETCOOL system: the air ducts are invisible within the room and only the air diffusers are unobtrusively integrated into the concrete ceiling or corridor partition wall. Additional ventilation ducts under the ceiling are therefore not necessary. The Kiefer air diffusers can be visually adjusted to suit the design concept for the building project. Architects in particular appreciate this aspect of the system.

A rethink is required: long-term solutions for a sustainable future
There are multiple requirements to satisfy for the future: ensuring a hygienic supply of fresh air in classrooms while also taking into consideration the EnEV stipulations on energy savings. The German Environment Agency’s Indoor Air Hygiene Commission (IRK) therefore recommends systems like CONCRETCOOL as the state of the art for future new school buildings. Current projects such as the Türli school in Switzerland, the Wetzlar campus consisting of the Goethe and Theodor Heuss schools, and the Unna campus utilise the tried and trusted ventilation concept from Kiefer Klimatechnik for new school buildings. The CONCRETCOOL system ensures that there is always a sufficient proportion of hygienic, fresh air available to comply with limits on CO₂. The combination of supply air and an activated ceiling for cooling also provides a comfortable climate, while fulfilling all important factors for hygienic, uninterrupted learning in a pleasant environment and achieving high energy efficiency.